BA 216 then BA 338 at Heathrow
Washington → London → Nice
Timetable, London time
06:15BA 216 from Washington at the gate
06:00BA 338 to Nice leaves the gate
23 h 45 apart on the timetable, overnight
BA 338 leaves 23 h 45 after BA 216 arrives on the timetable: more than half a day, so not a connection we count.